Different versions of machines for the manufacture and filling of mesh or net bags with fruit and vegetable products are known. These machines comprise a loading tube receiving the coupling of a tubular net loading unit, also called tube load, the mentioned tubular net being arranged around a gathered and longitudinally compacted loading tube, the length of which depends on the length of said loading tube and on the features of the mesh.
The tubular net is conventionally closed at its lower end, immediately below the lower mouth of the loading tube, to form the bottom of a bag which is then filled with the products which are introduced through the upper mouth of the tube and which fall by gravity inside it. The bag containing the products is finished and separated from the rest of the tubular net, the lower end of which is again closed to obtain another full bag, repeating the same operations again.
This type of machine must be periodically stopped so that the tube load is replaced, once out of tubular net, with another tube load that is loaded with a new tubular net.
The tube loads are coupled to the loading tube of the machine manually or by means of semiautomatic devices, but in any case the intervention of an operator is required.
For the purpose of maximally reducing these necessary stops which significantly affect the productivity of the machines and which require the supervision and intervention of an operator, machines have been disclosed that are provided with a loading tube and which similarly handle the tubular net during the manufacture and filling of the bags but in which, unlike the aforementioned machines, the tubular net is continuously developed, as the bags are manufactured, from a storage of mesh with great length in the form of a reel. The length of net conventionally wound in the form of a reel is much greater than the length of tubular net which can be gathered and longitudinally compacted in a tube load, being able to manufacture in the order of 2000 bags from the tubular net wound in a conventional reel, in comparison with approximately a hundred bags which can be manufactured from a standard tube load.
Patent documents EP 1053939 and EP 0315882 describe respective machines of this type comprising a vertical loading tube on which the tubular net which is drawn from a winding in the form of a reel is externally slid as the bags are manufactured. The machines are provided with drive means for the tubular net basically formed by inner rollers assembled in two of the opposite faces of the loading tube and corresponding outer support rollers, on which the mentioned inner rollers rest and between which the tubular net passes. The machines are furthermore provided with supplementary drive means for driving the tubular net, configured by way of an endless belt in the case of document EP 1053939 and rotating rollers in document EP 0315882, applied on the outer faces of the loading tube with the interposition of the tubular net.
In both machines, in the proximity of the lower mouth of the loading tube the latter is provided with a side opening through which the products to be packaged are introduced. To introduce said products in the bottom of the bag in the course of manufacture, a side opening is made in the portion of the tubular net covering the side opening of the loading tube, the operation being repeated every time a new section of tubular net is drawn from the reel, i.e., for each of the manufactured bags, when the side opening of the loading tube is covered again.
This slows down the speed of the machine while at the same time making it necessary to introduce an extra operation to close the side opening made in the tubular net after the introduction of the products in the bag in the course of manufacture precisely through said side opening.
As an alternative to these machines, patent document ES 2182664 describes a machine similar to the aforementioned ones but in which a continuous longitudinal cut is made along the entire tubular net as the latter slides on the loading tube. The cut made causes an opening in the net, suitable for introducing the products through said opening and through a side opening provided for such purpose in the loading tube, but it inevitably forces closing the tubular net again after introducing the products inside the loading tube before the tubular net slides below the level of the mouth of said loading tube. This operation has been proven to be very complicated technically, while at the same time it continues to involve a reduction in the operating speed of the machine. Furthermore, the bag finally obtained has a longitudinal seam along the entire length of the bag, which deteriorates its finish or makes the incorporation of a strip of flexible material to the bag necessary to cover said seam.
Therefore, an objective of the present invention is to disclose a process, a system and a machine that allow the continuous manufacture of bags from a storage of tubular net with great length, such as that of a storage in the form of a winding or reel, which solves the drawbacks of the known processes and of the known machines for putting them into practice.